The invention relates to a process for removing impurities dissolved in water, and more particularly organic nitrogen compounds, nitrates, nitrites and ammonium compounds utilising biological processes and to an apparatus for performing this process.
Processes for the purification of water by removing the above-mentioned impurities have hitherto only been known in connection with the slow process of natural ecological systems (Kusnezow, S. I. "Die Rolle der Mikroorganismen im Stoffkreislauf der Seen", 1959, VEB, Deutscher Verlag der Wissenschaften, Berlin) and have correspondingly been used hitherto in the case of so-called slow filters in connection with hydroeconomy for obtaining drinking water.
Individual stages of these processes are also carried out in laboratory tests for micro-biological teaching purposes as a proof of the physiological metabolism of mirco-organisms (Drews. G., 1968, "Mikrobiologisches Praktikum fur Naturwissenschaftler." Springer-Verlag, Berlin, Heidelberg, New York;) for water-purification purposes in the activated sludge of sewage treatment plants; (REHM, H. J., "Einfuhrung in die industrielle Mikrobiologie." 1971, Springer-Verlag, Berlin, Heidelberg, New York;) and in aquarium technology: HIRAYAMA, K., "Studies on Water control by filtration through sand bed in a marine aquarium with closed circulating system, 1965, I. Oxygen consumption during filtration as an index in evaluating the degree of purification of breeding water."; Bull. Jap. Sec. Sei. Fish. 31, pp. 977-982 and SAEKI, A., 1958, "Studies on fish culture in filtered closed-circulation aquaria. I. Fundamental theory and system design Standards"; Bull. Jap. Soc. Sei. Fish. 23, pp. 684-965 (Translation in D. Res. Bd. Canada 1964).
With the exception of slow filters the processes hitherto used for water purification purposes are not able to decompose nitrates, so that the water cannot be used as drinking water. Processes involving the use of slow filters ensure an adequate purification of the water through the removal of nitrates but they do not satisfy economic requirements because the purification process takes an unsatisfactorily long time and is also comparatively expensive. Therefore this process cannot be economically used for solving the problem arising in connection with the increased water consumption in all industrial countries.
On the basis of the above prior art, the problem of the present invention is to provide a process which compared with the hitherto known processes of this type can be operated in a shorter time with a lower energy consumption and with minimum mechanical expenditure, together with an apparatus for performing this process.